A man accused of illegally selling to Iran U.S.-made parts found in deadly explosives in Iraq faced charges in a federal court in Washington, the Justice Department has said.

Lim Yong Nam, 42, also known as Steven Lim, entered a not guilty plea and was ordered held without bond on April 4 for sending radio-frequency modules from the U.S. state of Minnesota to Iran between 2007 and 2008, violating a U.S. trade embargo.

The parts were later found in unexploded improvised explosive devices in Iraq by U.S. coalition forces.

The devices caused the majority of the casualties against Americans fighting in Iraq between 2003 and 2011, according to the U.S. indictment, which was originally filed in 2010.

The department said Lim and several co-conspirators had routed 6,000 radio-frequency modules to Iran through Singapore, 16 of which were discovered in Iraq.

U.S. officials have blamed Iran for supplying Shi'ite militias with lethal explosives directed against U.S. service members in Iraq. Iran has said the claims are baseless.

"The illegal export of restricted U.S. technology is extremely harmful to our national security," said Michael Steinbach, the executive assistant director of the FBI's national security branch.

"In this case the technology had lethal applications and was used in improvised explosive devices in Iraq, which endangered U.S. and coalition forces."

Lim, originally from Singapore, had been detained in Indonesia since October 2014. After a long investigative process, he was extradited to the United States to face charges, the department said.